A so-called “rear view monitor system” has been widespread in recent years, whereby an image taken by imaging means mounted on the back or elsewhere of a car is displayed by displaying means in the car, with an aim to perceive the situation of blind areas from the driver's seat of the car. Moreover, an “around view monitor system” is also becoming popular, which can display a simulated image of the car viewed from directly above, by processing and combining images taken from a total of four imaging means respectively mounted on the back, front, left, and right sides of the car.
Camera modules are widely used as the imaging means of such rear/around view monitor systems. Patent Literature 1 discloses one example of a camera module (see FIGS. 5A and 5B of the present application). The camera module disclosed in Patent Literature 1 is configured to have a lens unit 100 and an imaging element 400 inside a base part 200 that is formed hermetically by a front base part 200a and a rear base part 200b to take images by the lens exposed at an opening 300. The disclosure shows use of ultrasonic welding as one example of a method of firmly joining the front base part 200a and the rear base part 200b (paragraph 0037, Patent Literature 1).
In the camera module disclosed in Patent Literature 1, joint surfaces between the front base part 200a and the rear base part 200b are parallel to a plane orthogonal to the optical axis direction of the lens unit 100 (left and right direction on the paper plane of FIG. 5B of the present application).